/* gzlib.c -- zlib functions common to reading and writing gzip files
 * Copyright (C) 2004, 2010, 2011, 2012 Mark Adler
 * For conditions of distribution and use, see copyright notice in zlib.h
 */

#include "gzguts.h"

#if defined(_WIN32) && !defined(__BORLANDC__)
	#define LSEEK _lseeki64
#else
	#if defined(_LARGEFILE64_SOURCE) && _LFS64_LARGEFILE-0
		#define LSEEK lseek64
	#else
		#define LSEEK lseek
	#endif
#endif

/* Local functions */
local void gz_reset OF( ( gz_statep ) );
local gzFile gz_open OF( ( const void*, int, const char* ) );

#if defined UNDER_CE

/* Map the Windows error number in ERROR to a locale-dependent error message
   string and return a pointer to it.  Typically, the values for ERROR come
   from GetLastError.

   The string pointed to shall not be modified by the application, but may be
   overwritten by a subsequent call to gz_strwinerror

   The gz_strwinerror function does not change the current setting of
   GetLastError. */
char ZLIB_INTERNAL* gz_strwinerror( error )
DWORD error;
{
	static char buf[1024];

	wchar_t* msgbuf;
	DWORD lasterr = GetLastError();
	DWORD chars = FormatMessage( FORMAT_MESSAGE_FROM_SYSTEM
								 | FORMAT_MESSAGE_ALLOCATE_BUFFER,
								 NULL,
								 error,
								 0, /* Default language */
								 ( LPVOID )&msgbuf,
								 0,
								 NULL );
	if( chars != 0 )
	{
		/* If there is an \r\n appended, zap it.  */
		if( chars >= 2
				&& msgbuf[chars - 2] == '\r' && msgbuf[chars - 1] == '\n' )
		{
			chars -= 2;
			msgbuf[chars] = 0;
		}

		if( chars > sizeof( buf ) - 1 )
		{
			chars = sizeof( buf ) - 1;
			msgbuf[chars] = 0;
		}

		wcstombs( buf, msgbuf, chars + 1 );
		LocalFree( msgbuf );
	}
	else
	{
		sprintf( buf, "unknown win32 error (%ld)", error );
	}

	SetLastError( lasterr );
	return buf;
}

#endif /* UNDER_CE */

/* Reset gzip file state */
local void gz_reset( state )
gz_statep state;
{
	state->x.have = 0;              /* no output data available */
	if( state->mode == GZ_READ )    /* for reading ... */
	{
		state->eof = 0;             /* not at end of file */
		state->past = 0;            /* have not read past end yet */
		state->how = LOOK;          /* look for gzip header */
	}
	state->seek = 0;                /* no seek request pending */
	gz_error( state, Z_OK, NULL );  /* clear error */
	state->x.pos = 0;               /* no uncompressed data yet */
	state->strm.avail_in = 0;       /* no input data yet */
}

/* Open a gzip file either by name or file descriptor. */
local gzFile gz_open( path, fd, mode )
const void* path;
int fd;
const char* mode;
{
	gz_statep state;
	size_t len;
	int oflag;
#ifdef O_CLOEXEC
	int cloexec = 0;
#endif
#ifdef O_EXCL
	int exclusive = 0;
#endif

	/* check input */
	if( path == NULL )
	{
		return NULL;
	}

	/* allocate gzFile structure to return */
	state = malloc( sizeof( gz_state ) );
	if( state == NULL )
	{
		return NULL;
	}
	state->size = 0;            /* no buffers allocated yet */
	state->want = GZBUFSIZE;    /* requested buffer size */
	state->msg = NULL;          /* no error message yet */

	/* interpret mode */
	state->mode = GZ_NONE;
	state->level = Z_DEFAULT_COMPRESSION;
	state->strategy = Z_DEFAULT_STRATEGY;
	state->direct = 0;
	while( *mode )
	{
		if( *mode >= '0' && *mode <= '9' )
		{
			state->level = *mode - '0';
		}
		else
			switch( *mode )
			{
				case 'r':
					state->mode = GZ_READ;
					break;
#ifndef NO_GZCOMPRESS
				case 'w':
					state->mode = GZ_WRITE;
					break;
				case 'a':
					state->mode = GZ_APPEND;
					break;
#endif
				case '+':       /* can't read and write at the same time */
					free( state );
					return NULL;
				case 'b':       /* ignore -- will request binary anyway */
					break;
#ifdef O_CLOEXEC
				case 'e':
					cloexec = 1;
					break;
#endif
#ifdef O_EXCL
				case 'x':
					exclusive = 1;
					break;
#endif
				case 'f':
					state->strategy = Z_FILTERED;
					break;
				case 'h':
					state->strategy = Z_HUFFMAN_ONLY;
					break;
				case 'R':
					state->strategy = Z_RLE;
					break;
				case 'F':
					state->strategy = Z_FIXED;
				case 'T':
					state->direct = 1;
				default:        /* could consider as an error, but just ignore */
					;
			}
		mode++;
	}

	/* must provide an "r", "w", or "a" */
	if( state->mode == GZ_NONE )
	{
		free( state );
		return NULL;
	}

	/* can't force transparent read */
	if( state->mode == GZ_READ )
	{
		if( state->direct )
		{
			free( state );
			return NULL;
		}
		state->direct = 1;      /* for empty file */
	}

	/* save the path name for error messages */
#ifdef _WIN32
	if( fd == -2 )
	{
		len = wcstombs( NULL, path, 0 );
		if( len == ( size_t ) - 1 )
		{
			len = 0;
		}
	}
	else
#endif
		len = strlen( path );
	state->path = malloc( len + 1 );
	if( state->path == NULL )
	{
		free( state );
		return NULL;
	}
#ifdef _WIN32
	if( fd == -2 )
		if( len )
		{
			wcstombs( state->path, path, len + 1 );
		}
		else
		{
			*( state->path ) = 0;
		}
	else
#endif
		strcpy( state->path, path );

	/* compute the flags for open() */
	oflag =
#ifdef O_LARGEFILE
		O_LARGEFILE |
#endif
#ifdef O_BINARY
		O_BINARY |
#endif
#ifdef O_CLOEXEC
		( cloexec ? O_CLOEXEC : 0 ) |
#endif
		( state->mode == GZ_READ ?
		  O_RDONLY :
		  ( O_WRONLY | O_CREAT |
#ifdef O_EXCL
			( exclusive ? O_EXCL : 0 ) |
#endif
			( state->mode == GZ_WRITE ?
			  O_TRUNC :
			  O_APPEND ) ) );

	/* open the file with the appropriate flags (or just use fd) */
	state->fd = fd > -1 ? fd : (
#ifdef _WIN32
					fd == -2 ? _wopen( path, oflag, 0666 ) :
#endif
					open( path, oflag, 0666 ) );
	if( state->fd == -1 )
	{
		free( state->path );
		free( state );
		return NULL;
	}
	if( state->mode == GZ_APPEND )
	{
		state->mode = GZ_WRITE;    /* simplify later checks */
	}

	/* save the current position for rewinding (only if reading) */
	if( state->mode == GZ_READ )
	{
		state->start = LSEEK( state->fd, 0, SEEK_CUR );
		if( state->start == -1 )
		{
			state->start = 0;
		}
	}

	/* initialize stream */
	gz_reset( state );

	/* return stream */
	return ( gzFile )state;
}

/* -- see zlib.h -- */
gzFile ZEXPORT gzopen( path, mode )
const char* path;
const char* mode;
{
	return gz_open( path, -1, mode );
}

/* -- see zlib.h -- */
gzFile ZEXPORT gzopen64( path, mode )
const char* path;
const char* mode;
{
	return gz_open( path, -1, mode );
}

/* -- see zlib.h -- */
gzFile ZEXPORT gzdopen( fd, mode )
int fd;
const char* mode;
{
	char* path;         /* identifier for error messages */
	gzFile gz;

	if( fd == -1 || ( path = malloc( 7 + 3 * sizeof( int ) ) ) == NULL )
	{
		return NULL;
	}
	sprintf( path, "<fd:%d>", fd ); /* for debugging */
	gz = gz_open( path, fd, mode );
	free( path );
	return gz;
}

/* -- see zlib.h -- */
#ifdef _WIN32
gzFile ZEXPORT gzopen_w( path, mode )
const wchar_t* path;
const char* mode;
{
	return gz_open( path, -2, mode );
}
#endif

/* -- see zlib.h -- */
int ZEXPORT gzbuffer( file, size )
gzFile file;
unsigned size;
{
	gz_statep state;

	/* get internal structure and check integrity */
	if( file == NULL )
	{
		return -1;
	}
	state = ( gz_statep )file;
	if( state->mode != GZ_READ && state->mode != GZ_WRITE )
	{
		return -1;
	}

	/* make sure we haven't already allocated memory */
	if( state->size != 0 )
	{
		return -1;
	}

	/* check and set requested size */
	if( size < 2 )
	{
		size = 2;    /* need two bytes to check magic header */
	}
	state->want = size;
	return 0;
}

/* -- see zlib.h -- */
int ZEXPORT gzrewind( file )
gzFile file;
{
	gz_statep state;

	/* get internal structure */
	if( file == NULL )
	{
		return -1;
	}
	state = ( gz_statep )file;

	/* check that we're reading and that there's no error */
	if( state->mode != GZ_READ ||
			( state->err != Z_OK && state->err != Z_BUF_ERROR ) )
	{
		return -1;
	}

	/* back up and start over */
	if( LSEEK( state->fd, state->start, SEEK_SET ) == -1 )
	{
		return -1;
	}
	gz_reset( state );
	return 0;
}

/* -- see zlib.h -- */
z_off64_t ZEXPORT gzseek64( file, offset, whence )
gzFile file;
z_off64_t offset;
int whence;
{
	unsigned n;
	z_off64_t ret;
	gz_statep state;

	/* get internal structure and check integrity */
	if( file == NULL )
	{
		return -1;
	}
	state = ( gz_statep )file;
	if( state->mode != GZ_READ && state->mode != GZ_WRITE )
	{
		return -1;
	}

	/* check that there's no error */
	if( state->err != Z_OK && state->err != Z_BUF_ERROR )
	{
		return -1;
	}

	/* can only seek from start or relative to current position */
	if( whence != SEEK_SET && whence != SEEK_CUR )
	{
		return -1;
	}

	/* normalize offset to a SEEK_CUR specification */
	if( whence == SEEK_SET )
	{
		offset -= state->x.pos;
	}
	else if( state->seek )
	{
		offset += state->skip;
	}
	state->seek = 0;

	/* if within raw area while reading, just go there */
	if( state->mode == GZ_READ && state->how == COPY &&
			state->x.pos + offset >= 0 )
	{
		ret = LSEEK( state->fd, offset - state->x.have, SEEK_CUR );
		if( ret == -1 )
		{
			return -1;
		}
		state->x.have = 0;
		state->eof = 0;
		state->past = 0;
		state->seek = 0;
		gz_error( state, Z_OK, NULL );
		state->strm.avail_in = 0;
		state->x.pos += offset;
		return state->x.pos;
	}

	/* calculate skip amount, rewinding if needed for back seek when reading */
	if( offset < 0 )
	{
		if( state->mode != GZ_READ )        /* writing -- can't go backwards */
		{
			return -1;
		}
		offset += state->x.pos;
		if( offset < 0 )                    /* before start of file! */
		{
			return -1;
		}
		if( gzrewind( file ) == -1 )        /* rewind, then skip to offset */
		{
			return -1;
		}
	}

	/* if reading, skip what's in output buffer (one less gzgetc() check) */
	if( state->mode == GZ_READ )
	{
		n = GT_OFF( state->x.have ) || ( z_off64_t )state->x.have > offset ?
			( unsigned )offset : state->x.have;
		state->x.have -= n;
		state->x.next += n;
		state->x.pos += n;
		offset -= n;
	}

	/* request skip (if not zero) */
	if( offset )
	{
		state->seek = 1;
		state->skip = offset;
	}
	return state->x.pos + offset;
}

/* -- see zlib.h -- */
z_off_t ZEXPORT gzseek( file, offset, whence )
gzFile file;
z_off_t offset;
int whence;
{
	z_off64_t ret;

	ret = gzseek64( file, ( z_off64_t )offset, whence );
	return ret == ( z_off_t )ret ? ( z_off_t )ret : -1;
}

/* -- see zlib.h -- */
z_off64_t ZEXPORT gztell64( file )
gzFile file;
{
	gz_statep state;

	/* get internal structure and check integrity */
	if( file == NULL )
	{
		return -1;
	}
	state = ( gz_statep )file;
	if( state->mode != GZ_READ && state->mode != GZ_WRITE )
	{
		return -1;
	}

	/* return position */
	return state->x.pos + ( state->seek ? state->skip : 0 );
}

/* -- see zlib.h -- */
z_off_t ZEXPORT gztell( file )
gzFile file;
{
	z_off64_t ret;

	ret = gztell64( file );
	return ret == ( z_off_t )ret ? ( z_off_t )ret : -1;
}

/* -- see zlib.h -- */
z_off64_t ZEXPORT gzoffset64( file )
gzFile file;
{
	z_off64_t offset;
	gz_statep state;

	/* get internal structure and check integrity */
	if( file == NULL )
	{
		return -1;
	}
	state = ( gz_statep )file;
	if( state->mode != GZ_READ && state->mode != GZ_WRITE )
	{
		return -1;
	}

	/* compute and return effective offset in file */
	offset = LSEEK( state->fd, 0, SEEK_CUR );
	if( offset == -1 )
	{
		return -1;
	}
	if( state->mode == GZ_READ )            /* reading */
	{
		offset -= state->strm.avail_in;    /* don't count buffered input */
	}
	return offset;
}

/* -- see zlib.h -- */
z_off_t ZEXPORT gzoffset( file )
gzFile file;
{
	z_off64_t ret;

	ret = gzoffset64( file );
	return ret == ( z_off_t )ret ? ( z_off_t )ret : -1;
}

/* -- see zlib.h -- */
int ZEXPORT gzeof( file )
gzFile file;
{
	gz_statep state;

	/* get internal structure and check integrity */
	if( file == NULL )
	{
		return 0;
	}
	state = ( gz_statep )file;
	if( state->mode != GZ_READ && state->mode != GZ_WRITE )
	{
		return 0;
	}

	/* return end-of-file state */
	return state->mode == GZ_READ ? state->past : 0;
}

/* -- see zlib.h -- */
const char* ZEXPORT gzerror( file, errnum )
gzFile file;
int* errnum;
{
	gz_statep state;

	/* get internal structure and check integrity */
	if( file == NULL )
	{
		return NULL;
	}
	state = ( gz_statep )file;
	if( state->mode != GZ_READ && state->mode != GZ_WRITE )
	{
		return NULL;
	}

	/* return error information */
	if( errnum != NULL )
	{
		*errnum = state->err;
	}
	return state->msg == NULL ? "" : state->msg;
}

/* -- see zlib.h -- */
void ZEXPORT gzclearerr( file )
gzFile file;
{
	gz_statep state;

	/* get internal structure and check integrity */
	if( file == NULL )
	{
		return;
	}
	state = ( gz_statep )file;
	if( state->mode != GZ_READ && state->mode != GZ_WRITE )
	{
		return;
	}

	/* clear error and end-of-file */
	if( state->mode == GZ_READ )
	{
		state->eof = 0;
		state->past = 0;
	}
	gz_error( state, Z_OK, NULL );
}

/* Create an error message in allocated memory and set state->err and
   state->msg accordingly.  Free any previous error message already there.  Do
   not try to free or allocate space if the error is Z_MEM_ERROR (out of
   memory).  Simply save the error message as a static string.  If there is an
   allocation failure constructing the error message, then convert the error to
   out of memory. */
void ZLIB_INTERNAL gz_error( state, err, msg )
gz_statep state;
int err;
const char* msg;
{
	/* free previously allocated message and clear */
	if( state->msg != NULL )
	{
		if( state->err != Z_MEM_ERROR )
		{
			free( state->msg );
		}
		state->msg = NULL;
	}

	/* if fatal, set state->x.have to 0 so that the gzgetc() macro fails */
	if( err != Z_OK && err != Z_BUF_ERROR )
	{
		state->x.have = 0;
	}

	/* set error code, and if no message, then done */
	state->err = err;
	if( msg == NULL )
	{
		return;
	}

	/* for an out of memory error, save as static string */
	if( err == Z_MEM_ERROR )
	{
		state->msg = ( char* )msg;
		return;
	}

	/* construct error message with path */
	if( ( state->msg = malloc( strlen( state->path ) + strlen( msg ) + 3 ) ) == NULL )
	{
		state->err = Z_MEM_ERROR;
		state->msg = ( char* )"out of memory";
		return;
	}
	strcpy( state->msg, state->path );
	strcat( state->msg, ": " );
	strcat( state->msg, msg );
	return;
}

#ifndef INT_MAX
/* portably return maximum value for an int (when limits.h presumed not
   available) -- we need to do this to cover cases where 2's complement not
   used, since C standard permits 1's complement and sign-bit representations,
   otherwise we could just use ((unsigned)-1) >> 1 */
unsigned ZLIB_INTERNAL gz_intmax()
{
	unsigned p, q;

	p = 1;
	do
	{
		q = p;
		p <<= 1;
		p++;
	}
	while( p > q );
	return q >> 1;
}
#endif
